I actually started on a X/Brigade to Unity. One problem is that, while X converted up to Admiralty, and then to Nova (it did get shaky by that point), there's no good conversion to Unity. One of the major issues is that there's a lot of traits that don't convert/exist in Unity. The best you could do would be to bring them up to Admiralty, then use the guidelines in Unity to run them against other Unity ships.

I think a better approach would be to take X/Brigade ships and rebuild them in Unity from the ground up; will be cleaner from my experience.